| Message ID | 000c01d2754d$59a4cd70$0cee6850$@ru (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
Pavel Dovgalyuk <dovgaluk@ispras.ru> writes: >> From: Alex Bennée [mailto:alex.bennee@linaro.org] >> Pavel Dovgalyuk <dovgaluk@ispras.ru> writes: >> >> >> From: Alex Bennée [mailto:alex.bennee@linaro.org] >> > >> > Sorry, this is another problem which occurs only in icount replay mode: >> > 1. cpu_handle_exception tries to force exception when is cannot occur due to >> > running out all the planned instructions: >> > } else if (replay_has_exception() >> > && cpu->icount_decr.u16.low + cpu->icount_extra == 0) { >> > /* try to cause an exception pending in the log */ >> > cpu_exec_nocache(cpu, 1, tb_find(cpu, NULL, 0), true); >> > *ret = -1; >> > return true; >> > >> > 2. tb_find calls tb_gen_code, which cannot allocate new translation block >> > and calls tb_flush (which only queues the flushing) and cpu_loop_exit >> > 3. cpu_loop_exit returns to infinite loop of cpu_exec and the condition >> > if (cpu_handle_exception(cpu, &ret)) { >> > break; >> > } >> > is checked again causing an infinite loop. >> > >> > TB cache is not flushed because we never execute that break and real work of tb_flush >> > is made outside this loop. >> >> I think what we need is a: >> >> >> if (cpu->exit_request) >> break; > > Where this exit_request is supposed to be set? Ahh my mistake. Currently it is a global exit_request (becoming a per-cpu exit_request when MTTCG is merged). It's set by qemu_cpu_kick() when work is queued up, in this case the tb_flush async work. >> before the cpu_handle_exception() call to ensure any queued work gets >> processed first. Can you give me you current command line so I can >> reproduce this and check the fix works? > > I solved the problem using following patch: > > --- a/cpu-exec.c > +++ b/cpu-exec.c > @@ -451,6 +451,10 @@ static inline bool cpu_handle_exception(CPUState *cpu, int *ret) > #ifndef CONFIG_USER_ONLY > } else if (replay_has_exception() > && cpu->icount_decr.u16.low + cpu->icount_extra == 0) { > + /* Break the execution loop in case of running out of TB cache. > + This is needed to make flushing of the TB cache, because > + real flush is queued to be executed outside the cpu loop. */ > + cpu->exception_index = EXCP_INTERRUPT; > /* try to cause an exception pending in the log */ > cpu_exec_nocache(cpu, 1, tb_find(cpu, NULL, 0), true); > *ret = -1; I wonder if it worth renaming EXCP_INTERRUPT? I always get it confused with a guest interrupt. But the effect is the same as we set it on an exit_request. -- Alex Bennée
--- a/cpu-exec.c +++ b/cpu-exec.c @@ -451,6 +451,10 @@ static inline bool cpu_handle_exception(CPUState *cpu, int *ret) #ifndef CONFIG_USER_ONLY } else if (replay_has_exception() && cpu->icount_decr.u16.low + cpu->icount_extra == 0) { + /* Break the execution loop in case of running out of TB cache. + This is needed to make flushing of the TB cache, because + real flush is queued to be executed outside the cpu loop. */ + cpu->exception_index = EXCP_INTERRUPT; /* try to cause an exception pending in the log */ cpu_exec_nocache(cpu, 1, tb_find(cpu, NULL, 0), true); *ret = -1;